WF56: Mean Time Between Failure (MTBF)

Pre-Requisites

• A. RAM Module: access to Reliability, Availability & Maintainability (RAM) module enables Reliability Allocation.
• B. MADE Project: consists of FBD model items further defined with MTTF values.

Detailed Steps

1. Access Reliability Allocation (RA) Editor under 'Analyses' in the main menu bar.
2. Select the 'Plus' icon to create a new Mean Time Between Failure (MTBF) Allocation Analysis and define the analysis details (Analysis Name, Description, Target Item, Allocation Type) accordingly.
3. Set the Target Requirement and Design Margin by entering values in the text fields.
4. Decision — Weighted Analysis? If Weighted Allocation Type, there are additional values which can be modified; proceed to Step 5. If not, skip to Step 8.
5. Select the component from the table to enable modifiable fields.
6. Assign the appropriate MTBF Prediction value against the selected component.
7. Decision — All components weighted? Repeat Steps 5 and 6 until all component weightings are complete.
8. Select Calculate to run the analysis.
9. Review the analysis results.
10. Decision — Do you wish to apply the results to either System Model or an existing MCE analysis?
11. Select model items from the Analysis Results table to apply the results to the system model or an existing MCE. Select the "Apply to System Model" or "Apply to MCE" button to apply the calculated results to either System Model or MCE respectively.

Screen-by-screen detail (from embedded screenshots)

• Step 1: Access Reliability Allocation — Main menu: Analyses > Reliability Allocation Editor.
• Step 2: Create New MTBF Analysis — "Reliability Allocation" dialog, tabs: Reliability Allocation, MTBUM, MTBCF, MTBF. On MTBF tab: "MTBF Analysis Details" (Name e.g. "New MTBF Analysis", Description) and "MTBF Analysis" panel (Target Item e.g. "Power Generation" with Select... button; Allocation Type dropdown e.g. "Weighted (ARINC)" — "The MTBF of items is allocated in weighted distribution amongst the items in a level of indenture to satisfy the MTBF Requirement of the parent item."; Weighting Type dropdown e.g. "Historical Reliability Data" — "Weighting is automatically calculated based on the relative current MTTF values in the system model."). Click OK.
• Step 3: Enter Analysis Parameters — Tabs Analysis Configuration / Analysis Result. In Analysis Configuration: "MTBF Details" (MTBF Requirement e.g. 50000.00 hrs, Design Margin e.g. 10%); "Target Item" panel (read-only); Run Analysis panel with Calculate button; Requirements Verification Tool with "Export Requirement" button. Below, "Weighted Analysis Inputs" table with columns Item / MTBF Prediction (hrs) — example: Power Generation 97937.54, Control Unit 826044.00, Diesel Engine 125000.00, Air Filter through Secondary Fuel Filter all 1000000.00, Fuel Tank with Inlet/Lining/Outlet all 1000000.00.
• Step 5: Select Component from Analysis Inputs Table — Click a row in the table (e.g. "Air Filter") to select it.
• Step 6: Assign Weighting Values — "Item Weighting" panel: Selected Item field (e.g. "Air Filter"), MTBF Prediction field (e.g. 700000.00 hrs). Editing updates parent-level rollups (e.g. Power Generation becomes 93992.38, Diesel Engine becomes 118644.07).
• Step 9: Review Analysis Results — Click Calculate, view "Analysis Result" tab. Columns: Item, MTBF Prediction (h[rs]), Failure Rate Predicti[on], MTBF Weighting %, Allocated Failure Ra[te], Allocated MTTF (hrs). Example rows: Power Generation (93992.38, 10.6392, 90%, 18.00, 55555.56), Control Unit (826044.00, 1.2106, 10.24%, 2.0482, 488245.27), Diesel Engine (118644.07, 8.4286, 71.3%, 14.26, 70126.29), Air Filter (700000.00, 1.4286, 12.08%, 2.4169, 413745.14), other items each ~8.46% weighting with MTBF 1000000.00.
• Step 11: Select Applicable Model Items & Apply — In Analysis Result table, check desired items (e.g. Air Filter, Governor, Lift Pump checked) then click "Apply to System Model" or "Apply to MCE" to push the calculated results back.

Outputs

• I. Mean Time To Failure: average time a model item will be in operation before failing.